The Mysterious Tarantula

June 2011: It was the monsoon of 2007. After a heavy downpour the previous night, my colleague Rajesh Sanap and I began scouting the area near the New Zealand hostel in Aarey Milk Colony for a tarantula we had encountered every monsoon for the last several years. The identity of this tarantula had eluded us and we were determined to nail it this time. A close scrutiny of photographs in our collection suggested that it was a member of the family Theraphosidae, an exact dentification however, required more details. Armed with a flashlight, we concentrated on a tar road we knew was frequented by scorpions and within five minutes we got to see the first individual, a blackish-brown hairy spider and other critters!

Several photographs later, we decided to call it a night, confident that we had enough information to identify the species. However, a later examination of the images revealed that all the individuals we had observed were males. This was disappointing as several characteristics necessary for tarantula identification are specific to females. We would have to continue our search on subsequent visits.

The Aarey Milk Colony is situated in Goregaon East, a suburb of Mumbai. It covers an area of ca. 16 sq. km. on the southern border of the Sanjay Gandhi National Park (SGNP). Governed by the well known Dairy Cooperative of the National Dairy Development Board, the area is a grass and scrub habitat with a few hillocks, plus two perennial and one seasonal pond and many seasonal streams. Before it was cleared to cultivate the Marutian Para grass as fodder for cattle, the habitat was similar to that of SGNP. The original forest, though degraded, can still be seen here and there on some hillocks. The mix of highly varied habitat - scrub forest, hillocks, rocky outcrops, grass interrupted by human settlements - offers niches to a variety of lifeforms, making this a surprisingly diverse biodiversity hotspot, in the midst of Mumbai's concrete jungle. The forest here is mixed moist deciduous and is dominated by Mangifera indica, Gliricidia sepium, Delonix regia, Bombax ceiba and Eucalyptus melliodora with Tectona grandis, Butea monosperma, Pongamia pinnata, Cassia fistula… with Ziziphus sp. restricted to the hillocks.

MORE THAN TARANTULAS

That night as we made our way back along the beaten pathway, we stopped to photograph a burrowing frog. The woods were alive with the calls of cricket frogs, tree frogs and narrow-mouthed frogs. Our attention was soon drawn to a small lizard darting toward a heap of leaf litter. We removed leaf after leaf to have a closer look it was almost like unwrapping a present! And, after what seemed ages (in reality less than five minutes), Rajesh found the lizard hidden in a rolled-up leaf. It was the Kollegal ground gecko Geckoella collegalensis, an uncommon, ground-dwelling, impressive and strictly nocturnal reptile. By day it takes refuge under large boulders and emerges at dusk, where it can be seen along fire lines and forest paths that are clothed with a thick layer of leaf litter. This is where its food, primarily insects such as termites, can easily be found.

We also saw two scorpions, a large Heterometrus phipsoni, which had hidden under a boulder and a bark scorpion belonging to the genus Lychas.

ON THE HUNT

I am at home in Aarey and virtually every trip involves turning boulders, checking burrows lined with webs and other likely spider hideouts. Nevertheless, though we spotted several tarantulas, spiders, butterflies and other insects over several surveys, we did not find our target species. More than a challenge, this became an obsession. We began walking to the forested hillocks and other likely areas in Aarey every night after dinner. No one could accuse us of not being persistent! Interestingly, each night we managed to stumble on a species we had not previously seen in the area, including a Bombay caecilian Ichthyophis bombayensis, a colourful giant crab spider Heteropoda sp. and two scorpions Isometrus acanthurus and Hottentotta rugiscutis that had never been reported from Mumbai. Soon the monsoons passed and the ground dried up, which made the web-lined burrows more easily visible. But the several hundred burrows we checked turned out to be those of Chilobrachys fimbriatus and not the tarantula species we were looking for.

On subsequent surveys we recorded tarantulas such as C. fimbriatus, Plesiophrictus millardi and Indothele dumicola. In the first week of January 2008, on a hillock in the western part of Aarey near the Western Express highway, we discovered a burrow that had been destroyed with just 10 cm. of it intact. Soil in the area is often removed for brick making and in the process tarantula burrows are often destroyed or exposed. This tarantula's abdomen was partially exposed even as it sought to hide in what remained of its burrow.  Rajesh used a stick to nudge it out. The burrow was large and unlike any I had seen before. The spider's body habitus seemed thick and robust. After taking photographs, we released it and hurried home to refer to literature, hoping against hope that it was a female tarantula of the species we had been looking for.

It was!

The photographs enabled a positive identification - the tarantula was a member of the family Theraphosidae and subfamily Thrigmopoeinae. But we needed much more data to confirm whether the males we had found earlier belonged to the same species.

ONE AND ONE DOES NOT MAKE TWO!

By the end of the monsoon of 2009, we recorded 76 species of birds, 86 species of butterflies, five species of scorpions, 13 amphibians, 45 reptiles and more than 50 species of spiders belonging to at least 19 families. In addition we also listed 16 mammals! All in Aarey, an area most people tend to look down at as the “poor cousin" of the much richer and more grand SGNP with which it shares a boundary. All the while, we continued studying the Lychas sp., which we commonly encountered. After observing several individuals and consulting experts, we arrived at the conclusion that the specimen we had discovered was indeed a species undescribed by science earlier. Subsequently, we would name the species Lychas aareyensis after Aarey, the wild urban habitat that had offered it safe refuge all this while.

THE SEARCH HAD TAKEN US TWO YEARS

In December 2009, not surprisingly we both found ourselves in Aarey, doing what we loved best - turning rocks and spotting arachnids. Suddenly Rajesh asked me, “Are there trapdoor spiders in Aarey?" He had turned a rock to discover, to his utter surprise, a trapdoor burrow. We took photographs of the burrow entrance and began luring the owner out of its hideout. A few moments later a large robust female tarantula walked out of the burrow. And we were delighted to find that it was the same species we had found nearly two years ago at the brick-making site. The reason for its elusiveness was now clear -  trapdoor spider females spend their entire life in their burrows! Only the males leave the burrow at maturity… to search for mates.

Now that we had data on both the male and female we embarked on the task of identifying the species. Using the key provided by R. I. Pocock we were able to classify the male as Haploclastus validus and the female as H. robustus. Pocock named H. validus based on a male and H. robustus based on a female from Matheran. He had mistakenly classified the male and female of the same species as different species on account of the vast difference in their appearance. We were understandably excited. All details of our findings were forwarded to Dr. Manju Siliwal, a well-known arachnologist working at the Wildlife Information Liaison Development Society, Coimbatore. She confirmed that both indeed belonged to a single species.

Based on our study in Aarey, we were able to conclude that the H. validus and H. robustus, previously thought to be two different spiders, were actually a single species that we identified as the strong trapdoor tarantula Haploclastus validus. We had solved the mystery of the obscure tarantula but it was an experience that humbled us - here was proof that our knowledge of the natural world, especially of invertebrates like spiders and scorpions, was paltry at best.

While the Aarey Milk Colony may seem like a small denuded habitat unworthy of protection, it is in fact a veritable treasure trove of biodiversity particularly arachnids, herps and insects. Like all wilderness areas, it has clung to life and is extremely easy to regenerate - the place simply needs time to heal. Leopards are often reported in the colony. With necessary conservation measures, the Aarey Milk Colony could serve as an excellent living laboratory for wildlife students and enthusiasts, it simply needs to be given a fighting chance.

by Zeeshan A. Mirza